1. Field of the Invention
The present invention relates to exhaust gas sensors and, more particularly, to exhaust gas sensors that are mounted to an exhaust conduit of an exhaust system.
2. Description of the Related Art
Internal combustion engines typically power vehicles. Internal combustion engines output exhaust gases that contain combustion by-products. These exhaust gases often pass through an exhaust system before being expelled from the vehicle. Detectors often measure the concentration of oxygen in the exhaust gases so that the air-fuel ratio of the air-fuel mixture can be controlled based on an output from the detector. Typically, a detector is provided in an exhaust gas pipe of the exhaust gas system.
Personal watercraft or small planing boats often employ these detectors for measuring the concentration of oxygen in their exhaust gases. When used in these environments, the detector can be exposed to water as water can flow upstream (i.e., towards the internal combustion engine of the vehicle) through an exhaust gas pipe when, for example, the vehicle is turned over. Japanese Patent Publication No. Hei 11-13569 discloses an exhaust gas sensor designed to prevent a portion of the exhaust gas sensor from being exposed to water in the exhaust system.
Such exhaust gas sensors are often constructed by forming a chamber in the vicinity of an upper portion of a cylinder in the engine. The detecting component of the exhaust gas sensor protrudes in the upper section of the chamber. The chamber is typically in communication with the cylinder via an exhaust gas guide passage. An exhaust gas guide passage is connected to the bottom of the chamber at a position that is higher than the position where the cylinder is connected to the exhaust gas guide passage. The chamber is positioned away from the downstream portion of the exhaust gas pipe while the exhaust gas sensor is disposed at an upper position in the chamber. Thus, when water flows through the exhaust gas pipe towards the engine, the water may not reach the exhaust gas sensor. Also, since the exhaust gas guide passage is connected to the bottom of the chamber, even if water enters the chamber, it may be immediately discharged therefrom. Unfortunately, water can still reach the vicinity of the detecting part of the exhaust gas sensor. When the detecting part of the exhaust gas sensor gets wet with water, the accuracy of the exhaust gas sensor can be reduced, or the exhaust gas sensor can be damaged.